Economic Growth by Party

The best predictor of economic growth over a four year
presidential term is the party in the White house for that period.
From 1960 until 2004, the real GDP grew an average of 17%
during Democratic presidential terms, and an average of less than
12% during Republican presidential terms. The economy never
grew as rapidly as the Democratic average during any single
Republican 4-year term, and it never grew as slowly as the
Republican average during any single Democratic 4-year term.

There is less than one chance in 64 that these differences could
be caused by chance. More about this and other questions as to
causation at: Alternative Explanations.

Here are the growths of real Gross domestic product over the
four year terms. First, the terms with a Democrat in the White
House:

61 - 64

19.86%

65 - 68

21.81%

77 - 80

13.67%

93 - 96

13.53%

97 - 2000

17.87%

.

Mean

17.35%

SD

3.70%

"SD" is the (sample) standard deviation.

Then terms with Republican presidents:

69 - 72

12.38%

73 - 76

10.62%

81 - 84

12.63%

85 - 88

15.98%

89 - 92

8.81%

2001 - 2004

9.56%

.

Mean

11.66%

SD

2.60%

The mean for the entire period, 11 terms, is 13.86%; and the
standard deviation is 4.2%.